Hi Mike
It has been asked before over the years but I can’t honestly remember seeing a finished machine with that feature so it is difficult to say if it will get hot. Maybe someone else has.

The mounting face of the stepper will be bolted to a metal plate which will dissipate some heat.
To help the main body stay cool you could drill a large hole in the top and bottom surface of the section biased towards the rear end of the stepper to promote an updraft.
The motors run warm / slightly hot to the touch if they are being worked but that is in the open. Not trying to scare you but there is a temperature over which the stepper magnets break down. From memory I think it is 150deg? But if it is inside the box you won’t know.

So for small jobs I think it would be OK ( don’t hold me to it!) but an 8 hour run . . .